esm: add --experimental-import-non-javascript-without-assertion flag

doc/api/cli.md

@@ -251,6 +251,14 @@ added:
 
 Enable experimental `import.meta.resolve()` support.
 
+### `--experimental-import-non-javascript-without-assertion`
+<!-- YAML
+added: REPLACEME
+-->
+
+Enable experimental support importing non-JS modules without using an import
+assertion.
+
 ### `--experimental-json-modules`
 <!-- YAML
 added: v12.9.0

doc/api/errors.md

@@ -1109,6 +1109,14 @@ The JS execution context is not associated with a Node.js environment.
 This may occur when Node.js is used as an embedded library and some hooks
 for the JS engine are not set up properly.
 
+<a id="ERR_FAILED_IMPORT_ASSERTION"></a>
+### `ERR_FAILED_IMPORT_ASSERTION`
+<!-- YAML
+added: REPLACEME
+-->
+
+An import assertion has failed, preventing the specified module to be imported.
+
 <a id="ERR_FALSY_VALUE_REJECTION"></a>
 ### `ERR_FALSY_VALUE_REJECTION`
 
@@ -1660,6 +1668,14 @@ for more information.
 
 An invalid HTTP token was supplied.
 
+<a id="ERR_INVALID_IMPORT_ASSERTION"></a>
+### `ERR_INVALID_IMPORT_ASSERTION`
+<!-- YAML
+added: REPLACEME
+-->
+
+An import assertion is not supported by this version of Node.js.
+
 <a id="ERR_INVALID_IP_ADDRESS"></a>
 ### `ERR_INVALID_IP_ADDRESS`
 
@@ -1909,6 +1925,15 @@ strict compliance with the API specification (which in some cases may accept
 `func(undefined)` and `func()` are treated identically, and the
 [`ERR_INVALID_ARG_TYPE`][] error code may be used instead.
 
+<a id="ERR_MISSING_IMPORT_ASSERTION"></a>
+### `ERR_MISSING_IMPORT_ASSERTION`
+<!-- YAML
+added: REPLACEME
+-->
+
+An attempt was made to impor without an assertion a module that requires a
+specific import assertion to be loaded.
+
 <a id="ERR_MISSING_OPTION"></a>
 ### `ERR_MISSING_OPTION`
 

doc/api/esm.md

@@ -7,6 +7,9 @@
 <!-- YAML
 added: v8.5.0
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/39921
+    description: Add support for import assertions.
   - version:
     - REPLACEME
     pr-url: https://github.com/nodejs/node/pull/37468
@@ -230,6 +233,25 @@ absolute URL strings.
 import fs from 'node:fs/promises';
 ```
 
+## Import assertions
+<!-- YAML
+added: REPLACEME
+-->
+
+The [Import Assertions proposal][] adds an inline syntax for module import
+statements to pass on more information alongside the module specifier.
+
+```js
+import json from './foo.json' assert { type: "json" };
+await import('foo.json', { assert: { type: "json" } });
+```
+
+Node.js supports the following `type` values:
+
+| `type`   | Resolves to      |
+| -------- | ---------------- |
+| `"json"` | [JSON modules][] |
+
 ## Builtin modules
 
 [Core modules][] provide named exports of their public API. A
@@ -518,9 +540,8 @@ same path.
 
 Assuming an `index.mjs` with
 
-<!-- eslint-skip -->
 ```js
-import packageConfig from './package.json';
+import packageConfig from './package.json' assert { type: 'json' };
 ```
 
 The `--experimental-json-modules` flag is needed for the module
@@ -1351,6 +1372,8 @@ success!
 [Dynamic `import()`]: https://wiki.developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import#Dynamic_Imports
 [ECMAScript Top-Level `await` proposal]: https://github.com/tc39/proposal-top-level-await/
 [ES Module Integration Proposal for Web Assembly]: https://github.com/webassembly/esm-integration
+[Import Assertions proposal]: https://github.com/tc39/proposal-import-assertions
+[JSON modules]: #json-modules
 [Node.js Module Resolution Algorithm]: #resolver-algorithm-specification
 [Terminology]: #terminology
 [URL]: https://url.spec.whatwg.org/

doc/api/vm.md

@@ -54,6 +54,10 @@ executed in specific contexts.
 <!-- YAML
 added: v0.3.1
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/39921
+    description: Added suppoort of import assertions to the
+                 `importModuleDynamically` parameter.
   - version: v10.6.0
     pr-url: https://github.com/nodejs/node/pull/20300
     description: The `produceCachedData` is deprecated in favour of
@@ -91,6 +95,8 @@ changes:
     using it in a production environment.
     * `specifier` {string} specifier passed to `import()`
     * `script` {vm.Script}
+    * `import_assertions` {Object} The `"assert"` value passed to the
+      `optionExpression` optional parameter.
     * Returns: {Module Namespace Object|vm.Module} Returning a `vm.Module` is
       recommended in order to take advantage of error tracking, and to avoid
       issues with namespaces that contain `then` function exports.
@@ -642,6 +648,13 @@ The `vm.SourceTextModule` class provides the [Source Text Module Record][] as
 defined in the ECMAScript specification.
 
 ### `new vm.SourceTextModule(code[, options])`
+<!-- YAML
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/39921
+    description: Added suppoort of import assertions to the
+                 `importModuleDynamically` parameter.
+-->
 
 * `code` {string} JavaScript Module code to parse
 * `options`
@@ -667,6 +680,8 @@ defined in the ECMAScript specification.
     `import()` will reject with [`ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING`][].
     * `specifier` {string} specifier passed to `import()`
     * `module` {vm.Module}
+    * `import_assertions` {Object} The `"assert"` value passed to the
+      `optionExpression` optional parameter.
     * Returns: {Module Namespace Object|vm.Module} Returning a `vm.Module` is
       recommended in order to take advantage of error tracking, and to avoid
       issues with namespaces that contain `then` function exports.
@@ -852,6 +867,10 @@ const vm = require('vm');
 <!-- YAML
 added: v10.10.0
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/39921
+    description: Added suppoort of import assertions to the
+                 `importModuleDynamically` parameter.
   - version: v15.9.0
     pr-url: https://github.com/nodejs/node/pull/35431
     description: Added `importModuleDynamically` option again.
@@ -893,6 +912,8 @@ changes:
     considered stable.
     * `specifier` {string} specifier passed to `import()`
     * `function` {Function}
+    * `import_assertions` {Object} The `"assert"` value passed to the
+      `optionExpression` optional parameter.
     * Returns: {Module Namespace Object|vm.Module} Returning a `vm.Module` is
       recommended in order to take advantage of error tracking, and to avoid
       issues with namespaces that contain `then` function exports.
@@ -1068,6 +1089,10 @@ vm.measureMemory({ mode: 'detailed', execution: 'eager' })
 <!-- YAML
 added: v0.3.1
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/39921
+    description: Added suppoort of import assertions to the
+                 `importModuleDynamically` parameter.
   - version: v6.3.0
     pr-url: https://github.com/nodejs/node/pull/6635
     description: The `breakOnSigint` option is supported now.
@@ -1113,6 +1138,8 @@ changes:
     using it in a production environment.
     * `specifier` {string} specifier passed to `import()`
     * `script` {vm.Script}
+    * `import_assertions` {Object} The `"assert"` value passed to the
+      `optionExpression` optional parameter.
     * Returns: {Module Namespace Object|vm.Module} Returning a `vm.Module` is
       recommended in order to take advantage of error tracking, and to avoid
       issues with namespaces that contain `then` function exports.
@@ -1145,6 +1172,10 @@ console.log(contextObject);
 <!-- YAML
 added: v0.3.1
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/39921
+    description: Added suppoort of import assertions to the
+                 `importModuleDynamically` parameter.
   - version: v14.6.0
     pr-url: https://github.com/nodejs/node/pull/34023
     description: The `microtaskMode` option is supported now.
@@ -1211,6 +1242,8 @@ changes:
     using it in a production environment.
     * `specifier` {string} specifier passed to `import()`
     * `script` {vm.Script}
+    * `import_assertions` {Object} The `"assert"` value passed to the
+      `optionExpression` optional parameter.
     * Returns: {Module Namespace Object|vm.Module} Returning a `vm.Module` is
       recommended in order to take advantage of error tracking, and to avoid
       issues with namespaces that contain `then` function exports.
@@ -1247,6 +1280,10 @@ console.log(contextObject);
 <!-- YAML
 added: v0.3.1
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/39921
+    description: Added suppoort of import assertions to the
+                 `importModuleDynamically` parameter.
   - version: v6.3.0
     pr-url: https://github.com/nodejs/node/pull/6635
     description: The `breakOnSigint` option is supported now.
@@ -1290,6 +1327,8 @@ changes:
     using it in a production environment.
     * `specifier` {string} specifier passed to `import()`
     * `script` {vm.Script}
+    * `import_assertions` {Object} The `"assert"` value passed to the
+      `optionExpression` optional parameter.
     * Returns: {Module Namespace Object|vm.Module} Returning a `vm.Module` is
       recommended in order to take advantage of error tracking, and to avoid
       issues with namespaces that contain `then` function exports.

lib/internal/errors.js

@@ -953,6 +953,9 @@ E('ERR_ENCODING_NOT_SUPPORTED', 'The "%s" encoding is not supported',
   RangeError);
 E('ERR_EVAL_ESM_CANNOT_PRINT', '--print cannot be used with ESM input', Error);
 E('ERR_EVENT_RECURSION', 'The event "%s" is already being dispatched', Error);
+E('ERR_FAILED_IMPORT_ASSERTION', (request, key, expectedValue, actualValue) => {
+  return `Failed to load module "${request}", expected ${key} to be ${JSONStringify(expectedValue)}, got ${JSONStringify(actualValue)} instead`;
+}, TypeError);
 E('ERR_FALSY_VALUE_REJECTION', function(reason) {
   this.reason = reason;
   return 'Promise was rejected with falsy value';
@@ -1250,6 +1253,9 @@ E('ERR_INVALID_FILE_URL_HOST',
 E('ERR_INVALID_FILE_URL_PATH', 'File URL path %s', TypeError);
 E('ERR_INVALID_HANDLE_TYPE', 'This handle type cannot be sent', TypeError);
 E('ERR_INVALID_HTTP_TOKEN', '%s must be a valid HTTP token ["%s"]', TypeError);
+E('ERR_INVALID_IMPORT_ASSERTION',
+  (type, value) => `Invalid ${JSONStringify(type)} import assertion: ${JSONStringify(value)}`,
+  TypeError);
 E('ERR_INVALID_IP_ADDRESS', 'Invalid IP address: %s', TypeError);
 E('ERR_INVALID_MODULE_SPECIFIER', (request, reason, base = undefined) => {
   return `Invalid module "${request}" ${reason}${base ?
@@ -1394,6 +1400,9 @@ E('ERR_MISSING_ARGS',
     }
     return `${msg} must be specified`;
   }, TypeError);
+E('ERR_MISSING_IMPORT_ASSERTION',
+  'Failed to load %s: Node.js requires modules of format "%s" to be loaded ' +
+  'using an assertion "%s" with value "%s"', TypeError);
 E('ERR_MISSING_OPTION', '%s is required', TypeError);
 E('ERR_MODULE_NOT_FOUND', (path, base, type = 'package') => {
   return `Cannot find ${type} '${path}' imported from ${base}`;

lib/internal/modules/cjs/loader.js

@@ -1015,9 +1015,10 @@ function wrapSafe(filename, content, cjsModuleInstance) {
       filename,
       lineOffset: 0,
       displayErrors: true,
-      importModuleDynamically: async (specifier) => {
+      importModuleDynamically: async (specifier, _, import_assertions) => {
         const loader = asyncESM.esmLoader;
-        return loader.import(specifier, normalizeReferrerURL(filename));
+        return loader.import(specifier, normalizeReferrerURL(filename),
+                             import_assertions);
       },
     });
   }
@@ -1030,9 +1031,10 @@ function wrapSafe(filename, content, cjsModuleInstance) {
       '__dirname',
     ], {
       filename,
-      importModuleDynamically(specifier) {
+      importModuleDynamically(specifier, _, import_assertions) {
         const loader = asyncESM.esmLoader;
-        return loader.import(specifier, normalizeReferrerURL(filename));
+        return loader.import(specifier, normalizeReferrerURL(filename),
+                             import_assertions);
       },
     });
   } catch (err) {